Paul Testa from HEM Architects explains the difference between renovation and retrofit, using his own home as an example of a deep retrofit.

Interview with Paul Testa

Paul Testa is a director of HEM Architects in Sheffield. He’s been on the podcast before highlighting a few hidden costs you might experience on a house build project. Today he’s explaining some common terminology when it comes to altering homes: renovation, retrofit, remodel, extension and eco renovation.

While these words might seem self-explanatory they can get lumped together and we perhaps miss some of the nuances. So Paul is going to explain each term as well as share a few details from his own retrofit.

Renovation is about bringing your house back up to standard

A renovation is work that brings a house back up to a good standard. Not only will it be about making it look nice but it will deal with any disrepair, and perhaps replace the electrics and plumbing. New windows might be installed. It may also include putting in new kitchens and bathrooms, and then plastering and repainting.

Paul gives an example of buying a Victorian terrace that needs lots of work. You are renovating the house to bring it up to date and make it suitable for modern lifestyles.

Remodelling is rethinking how the spaces work

Remodelling is when you consider how the spaces work together at a more fundamental level. It’s not just about what the home looks like, but how the spaces are connected, maybe bringing multiple rooms into an open plan layout. Upstairs it may be about making better use of bathroom and bedroom spaces. It will likely involve moving internal doorways and removing walls, and whilst it could include external changes to doorways and windows this is less common.

Extensions are about creating more space

Extensions or additions are about adding more space. Sometimes a client may think they need more space but a remodel would actually solve the problem. Often extensions are needed as families grow or needs change. Paul says that it’s quite common for people to want a larger kitchen, dining space that faces onto the garden, which is very different from how houses were laid out in the past.

“We live very differently now, we congregate in our kitchens, and often remodelling can deal with that, but sometimes you do need to gain more space in that area to fully enjoy those benefits.”

Retrofit deals with performance

Retrofit is a holistic approach that improves the building fabric, making a space more comfortable, healthy and energy efficient. As part of this upgrade moisture will need to be managed and a good ventilation strategy is required.

Clients may have different drivers for carrying out this work, such as wanting consistent energy bills, so they are not so affected by energy price jumps, or increased comfort because they can’t get the house warm enough in the winter, or they may be motivated by reducing their carbon emissions.

With the right budget a retrofit can deal with all of these pain points but often work might have to be phased and the immediate solution will address the priority.

Doing work on your home locks in the performance for the coming years

While a renovation project might create a beautiful home it may not improve the performance at all and once the work is complete the homeowner is unlikely to want to make any significant changes for the foreseeable future. So this might lock in poor performance for a number of years.

The benefits of retrofit are ‘felt’ rather than seen

When a retrofit is complete it may look much the same as if renovation work had been carried out. The difference will be in how the building feels and performs.

The investment is going into modelling and understanding the initial home, developing detailed designs and then installing additional insulation and introducing an airtightness layer. High performance windows and doors will be added and ventilation will have to be addressed, often using mechanical ventilation with heat recovery (MVHR).

Paul retrofitted a 1970s semi-detached home

In 2013 Paul and his family bought a 1970s semi-detached house, which had a two storey side extension that was poorly laid out and a small sun room to the rear. The sun room was boiling in the summer and a cold store in the winter, and the main house was also freezing. This property was ripe for an intervention.

The harsh winter of 2013 was the driver to do something about it but it wasn’t until 2018 that work began. These processes take a long time and architects, much like builders, are always last in the queue.

Once the plans were formulated the main structural changes saw the original extension and old garage demolished. Although there would be a new single storey rear extension and a two storey side extension, overall there would only be 15m² of extra space (making the floor area 136m²) when compared to the existing dwelling.

Downstairs the suspended timber floor was removed and replaced with a concrete raft. This had between 20-70cm of insulation beneath it and provided both the new floor finish and also the structure for the extension to sit on (so there was no need for separate footings).

The extension is timber frame, with 140mm deep studs, insulated with mineral wool in between and then wood fibre on the outside of the studs and rafters.

The original house was insulated internally with wood fibre insulation and careful consideration was given to the thickness of this so that moisture is managed well and the risks of interstitial condensation are minimised.

If this condensation appeared inside the construction it would damage the fabric over time and potentially produce mould spores that will end up in the air.

The roof of the original house has also been well insulated with mineral wool and wood fibre.

When it comes to the windows, Paul used a mixture or inward and outward opening triple glazed units. The reason for this was because it depended whether the insulation was internal as in the main house or external as in the extensions.

Mechanical ventilation with heat recovery (MVHR) provides constant fresh air and Paul describes this as a game-changer.

“The house always feels fresh, we don’t have any condensation anywhere, and we’re not losing that heat. I think the MVHR also helps with heat distribution, as we don’t have many heat emitters in the house. In 2018/19, when we were doing this work heat pumps were not as readily available as now, so we chose a boiler with a hot water tank. It’s the smallest system boiler we could buy, so that it can modulate down low enough for our 2 kW heat demand or heat load. This provides the hot water and runs a radiator in the living room and towel radiators in the bathroom and shower rooms.”

Paul says that in the autumn and spring they don’t have the heating on at all. The house might be at 19C initially but by the time everyone is up and moving all the incidental heat gains (from activities such as showering and cooking) warm it up to 21C or 22C.

They also have a couple of portable panel heaters (30W each) that can be moved around the house as required.

Unfortunately Paul’s house did not reach the EnerPHit standard as the final airtightness test came in slightly above the required levels at 1.08 air changes per hour at 50 Pascals. Interestingly during the build process they were on track, with readings of around 0.7 air changes per hour at 50 Pascals.

This goes to show how important it is to get the team to protect the airtightness layer once it’s in place.

The space had to work well for the family and perform brilliantly

As this conversation has been around the nuances between renovation, retrofit, remodelling and extensions, we asked Paul what his priorities were as he considered his funds.

Our budget was fantastic for a renovation and remodelling project, but once you included the retrofit elements it was much more constrained. I wasn’t really willing to compromise on performance… I was also aware that whatever we were doing to the house we were likely to be investing more than the house was really worth. So it wasn’t about getting a monetary return but getting a return in terms of comfort and health.

Although the work did put the family under financial strain at the time they don’t have a huge mortgage and now they’ve got some control over their heating bills.

They also didn’t complete everything at the time and left some DIY jobs to tick off over the years.

Quality assurance is a big part of performance

If you can’t afford or don’t want to do a high performance retrofit you have to realise that there will be an impact on performance.

Paul says that if you’re adding space and extending you will need to meet building regulations which are better than they once were. The challenge is in making sure there is good workmanship on site so insulation is well installed and continuous. Moisture must also be considered and good ventilation is important.

Damp, mould and condensation are likely if you ‘just’ renovate

Just renovating an existing dwelling will not change the performance. So if there were problems with discomfort then they will still be there.

Paul has been to houses with brand new bathrooms and observed black mould around window frames. This is a sign that the moisture balance, ventilation and surface temperatures haven’t been considered.

Stripping back a building can help identify and fix problems

Quite often damp patches can stay hidden and you might not even realise you have a problem until something fails.

So major work is an opportunity to check that the home really is in good health.

National Retrofit Hub is providing a central Knowledge Hub to support all retrofitters

In terms of useful resources Paul suggests looking at the National Retrofit Hub, which aims to collaborate with those already carrying out retrofit projects, empower the next generation and facilitate retrofits in the UK.

It’s a nonprofit organisation that brings together all those involved in the retrofit sector to share their expertise and work together to enable a National Retrofit Strategy to be delivered.

It’s also teaming up with various organisations to reach architects and builders as well as those who might be considering a DIY approach.

Their goal is to see retrofit carried out at scale.

We have to start valuing health and comfort

The dial is moving slowly but we are starting to value good air quality and comfort in our homes. A few years ago internet speed was a more important factor!

Also, historically, energy has been cheap and it has been simpler to keep heating our leaky homes. However, we’ve already experienced sudden energy price hikes and this has forced people to become more aware of energy performance. Although this may not be translating into people investing large amounts to save money on heating bills it does mean they are paying more attention to energy performance and EPC certificates when buying houses.

Key challenges to consider for retrofit projects

Before you embark on a retrofit project the first thing is to make your home retrofit ready. Deal with leaky gutters, a roof in poor repair or bad pointing to make sure your home is in a good state first.

The second challenge is who to turn to for advice. You need to be sure that the advice is independent and solution agnostic. In other words you need to be careful the advice is not part of a sales pitch.

Paul mentions a few organisations and community interest companies around the UK:

• Loco Home Retrofit in Glasgow.
• People Powered Retrofit in Manchester.
• Association for Environmental Conscious Building.

Finally Paul underlines the importance of working with professionals who understand the moisture risks.

The newer the building that you’re working with, the less of a risk that is, but for example, with an old stone barn conversion you need to be aware of moisture risks. We’re now starting to see some retrofit assessors and retrofit designers who are specifically qualified in heritage buildings as well.

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